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Optically guided munition control system and method

Optically guided munition control system and method description/claims

This application claims rights under 35 USC 119(e) from U.S. application Ser. No. 60/650,718, filed Feb. 7, 2005; the contents of which are incorporated herein by reference.

1. Field of the Invention

The present invention relates to armaments and more particularly to guided munitions. More particularly, the invention relates to a system and method for optically guiding a munition following a ballistic path toward a target by processing optical signals from an optical source located at the target and controlling the roll of the munition to generate flight control signals fed to a plurality of flight control canards mounted on the munition.

2. Background Information

Mortars are one of the most commonly employed weapons in a ground combat unit. The traditional role of mortars has been to provide close and continuous fire support for maneuvering forces. Military history has repeatedly demonstrated the effectiveness of mortars. Their rapid, high-angle, plunging fires are invaluable against dug-in enemy troops and targets in defilade, which are not vulnerable to attack by direct fires. One of the major disadvantages of mortars is their comparatively low accuracy, and as a result mortars are becoming less effective in today's precision combat environment. Equipping a mortar round with a precision guidance package will increase its accuracy, enabling the mortar to be a precision munition that will be significantly more effective in wartime situations. For maximum utility, the guidance package preferably should be an inexpensive retrofit to current munitions, with a cost in production that allows its use in all situations, either as a guided or unguided weapon.

Unguided munitions are subject to aim error and wind disturbances. These often cause the munition to miss the target completely or require many rounds to complete the fire mission due to the large CEP (Circular Error Probability). Current approaches to guided weapons are expensive and are used on larger long range weapons. The approach of the present invention results in significantly lower cost and smaller size. This allows use with small to medium caliber weapons and significantly improves CEP which also results in a significant reduction in the quantity of rounds required to complete the fire mission which in turn results in lower overall cost and improved crew survivability. In addition, another benefit to this approach is the virtual elimination of collateral damage due to errant rounds impacting non-targeted areas.

Mortars, if guided at all, are guided by an expensive guidance and control (G&C) system. The cost is high for current guided mortars and unguided mortars have poor accuracy. Also, unguided mortars result in unacceptable collateral damage, excess cost due to large number of rounds required to blanket target area, and expose the mortar crew to counterbattery fire due to large time required to drop the necessary shells to saturate the target.

Existing prior art guidance systems and methods use algorithms that may be computationally inefficient, require excessive input information, are incompatible with new sensor designs and require expensive support hardware (seeker implementation).

Therefore, there is a need for an accurate and cost effective method for optically guiding munitions such as mortars. There is also a need for an ultra low cost G&C approach for mortars which is compatible with a large class of rounds. Furthermore, there is a need for a highly efficient detection/tracking algorithm compatible with optical hardware and limited processing capability associated with small caliber precision guided weapons design.

The present invention provides a computationally efficient method, algorithm, and implementation which is compatible with low cost optical seeker components and a low volume stability augmentation system to provide the necessary detection and processing capability to control a small caliber round thereby providing a cost effective guided munition. The technique of the present invention also is compatible with other munitions and applications, and is simple and robust with intrinsically low false alarm rate.

The present invention furthermore provides an algorithm for interface with an (IR) infrared (optic) seeker design which results in significant improvement in CEP and cost reduction.

Furthermore, the present invention provides a control and guidance system for a munition which mounts an optical seeker subsystem in the nose of the munition, which includes an optical array of photodetectors. The photodetectors receive tracking signals from an illuminator at a target, which signals are supplied to a processor subsystem, which in turn, provides steering signals to a plurality of canards. The canards provide up and down steering directions to correct for range errors of the munition and left/right steering directions to correct for lateral aiming areas. The canards change the ballistic path of the munition as it approaches the target to provide a more accurate circular error probability at the target.

Another aspect of the present invention is to provide the munition with an authentication code which must validate a code contained in the radiated signal from the illuminated target in order to arm the munition to ensure that the correct munition is being directed to a particular target.

A still further feature of the present invention is to provide the munition with a Ram Air Turbine which supplies a processor subsystem in the munition fuse with the flight time of the munition to apogee, which time is used to estimate the trajectory of the munition. The estimated trajectory is matched against allowed trajectories stored in the processor in order to determine the true angle of attack of the munition and provide up and down steering corrections to certain canards mounted on the nose of the munition for correcting any range error.

A further aspect of the invention is to provide a canard drive assembly with a three axis control mechanism, preferably comprised of four canards, two of which are controlled by a common shaft with the remaining two canards each being controlled by an independently driven shaft; and wherein the shafts are driven through a gear reduction mechanism to provide the desired transmission of power from the drive motors to the canards.

Still another feature of the present invention is to form the guidance and control system and the various subsystems thereof on printed circuit boards which are mounted in a compact condition in the replacement fuse of the munition, which enables the guidance and control system to withstand the various G forces exerted thereon during launch and ballistic flight toward the target.

A further aspect of the present invention is to enable the replacement fuse to be located within a nose housing attached to the usual body of the munition thereby avoiding any redesign or manner of use of the munition, enabling it to be launched by existing mortar launchers or other type of propelling mechanism.

Still another aspect of the present invention is to provide the control and guidance system with three MEMS gyros to sense the body yaw, pitch and roll. The gyros provide signals through a processor subsystem to a flight control subsystem to initially deroll the munition, afterwhich the range and aiming errors can be more easily corrected based upon the radiated signals from the illuminated target detected by the detector array of the optical seeker subsystem.

• Provisional Patent
• Utility Patent

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